Purifying used metalworking lubricating oils



United States Patent U.S. Cl. 208-180 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a process for treating lubricating oils of the types used in the working of ferrous and non-ferrous metals which are contaminated with finelydivided suspended solids exemplified by metal particles, metal oxides and dirt whereby such particles are agglomerated to a point whereby they are readily removed from the lubricating oils thereby allowing such oils to be reused, reclaimed and the like. The invention accomplishes this result by treating such contaminated oils with at least 50 p.p.m. of a trimerized polycarboxylic acid formed by the polymerization of a polyolefinic fatty acid which contains at least carbon atoms in aliphatic chain. The oils treated with the polymerized polyolefinic fatty acids are subjected to a mixing step whereby agglomeration of the finely-divided particles is achieved. The thus agglomerated particles removed from the oils by conventional purification systems whereby the oils are suitable for reuse in various metal-working operations.

INTRODUCTION Metalworking lubricants, cutting oils, grinding oils and the like are used extensively in both the ferrous and nonferrous metalworking industries. These lubricants are most frequently in the form of emulsions wherein a small quantity of oil is admixed with a large volume of water with such emulsions being used to lubricate, cool and condition metal being Worked upon by a variety of metalworking operations. One of the most common types of metalworking operations in which these emulsions are used is in the cold reduction of metals. In such reduction operations, it is necessary to supply both a coolant and a lubricant to the metal as it passes between the rolls in which the reduction takes place. The water supplies the cooling action and the oil supplies the lubrication. In such systems, after prolonged usage, the oil in the system tends to become contaminated with finely-divided metallic particles, finely-divided metal oxides and other extraneous material such as mill dirt and the like which tend to decrease the efiiciency and the activity of the oil as a lubricant.

When the oil becomes contaminated with metal particles, it is no longer useful as a lubricant due to its difficulty of reemulsification and also the metal contaminants and other suspended materials furnish a source of undesirable abrasive. If the metal contaminants can be readily removed from such oils, they can be reused whereby the cost of metalworking operations is reduced. When dirty oils and emulsion are discarded, not only are valuable chemical values lost, but it provides a source of contamination which tends to pollute rivers, lakes and streams. Many local regulations require that such contaminating practices be abolished. Therefore a serious disposal problem presents itself.

In large metalworking operations, it is often customary to establish reclaiming areas or systems for hydrocarbon lubricating oils used in the working of both ferrous and non-ferorus metals. In these systems the oils are separated from water when they are used in the form of an emulsion and then subjected to conventional purification steps, in an effort to remove the metal contaminants which tend to diminish the effectiveness of these oils as lubricants. Typical systems used to purify metalworking lubricants are filtration, centrifugation and, in some cases, magnetic separation. Of these purification systems, the most commonly used is filtration.

It has been discovered that when metalworking oils are contaminated with extremely finely-divided particles, the ability to remove these by filtration is oftentimes difficult. This is particularly true since many of the metal particles and other contaminants contained in the oil are in such a state of fine subdivision that the particles pass between the granules of the filter element and are not effectively removed thereby. These finely-divided metallic particles, when not completely removed by filtration, still cause the oil to be in a contaminated condition.

It is obvious that if the metallic contaminants, as well as other contaminants in oil which are in an extremely fine state of subdivision, could be agglomerated to a particle size whereby they could be readily acted upon by such purification systems as filters, magnetic separators, centrifuges and the like, improved reclaiming operations would be possible to achieve. If it were possible to improve the efficiency of particle removal from dirty metalworking lubricants, their usefulness in the standpoint of lubricant life would be materially improved thereby affording a large ecnomic advantage to the metalworking industry.

While it is customary to aggregate finely-divided solids in aqueous systems, there has been no real attempt in the art to apply aggregation technique by chemical means for treating oil which contain finely-divided particles. If it were possible to chemically treat oils containing finelydivided particles whereby these particles could be agglomerated into such a size that they could be readily removed, a valuable contribution to the metal-working art would be afforded. If such a chemical means for causing aggregation of finely-divided metal particles were avaliable, it should possess the following characteristics: (1) work readily on a variety of hydrocarbon oil lubricants; (2) work at low economic dosages; (3) be commercially available or be capable of ecoomic synthesis; (4) not interfere with the characteristics of the purified oil; and (5 beneficially add improved properties to the oil once it had acted upon the fiely-divided particles therein to improve agglomeration.

OBJECTS OF THE INVENTION Based on the above, it becomes therefore an object of the invention to provide an improved process for treating lubricating oils of the type used in the working of ferrous and non-ferrous metals which have been contaminated THE INVENTION In accordance with the invention, it has been found that lubricating oils of the types used in the working of ferrous and non-ferrous metals which are contaminated with finely-divided suspended solids exemplified by finelydivided metal particles, metal oxides and mill dirt may be subjected to a process which comprises the steps of treating such oils with at least 50 p.p.m. of a trimerized polycarboxylic acid formed by the polymerization of a polyolefinic fatty acid which contains at least 10 carbon atoms in an aliphatic chain. After treating the oil with the trimerized polycarboxylic acid, the oil is mixed, whereby the particle size of the suspended particles is caused to grow to a point where they may be readily removed by filtration and like means. This provides a reclaimed oil capable of reuse in metalworking operations. In a preferred embodiment of the invention, the mixing and agglomeration step outlined above is conducted at elevated temperatures, e.g. at least 100 F. and preferably at higher temperatures up to about the decomposition level of the particular trimerized polycarboxylic acid and the lubricant being treated.

The lubricating oils customarily used in the rolling of metals may be selected from a Wide group of organic compounds which contain basically in their molecular makeup, hydrocarbon groups. Typical of such hydrocarbon lubricants are various petroleum fractions, fatty acids, fatty acid esters, modified waxes, soaps and the like. For purposes of this disclosure, all such materials are considered to be lubricants which are used in the working of ferrous and non-ferrous metals.

As indicated, these lubricants are most commonly used as emulsions in many metalworking operations. They are used at dosage ranges of from about 1 to about 20% by weight of water, with typical emulsions, particularly those used in the cold reduction of metals such as steel being within the range of 310% by weight.

The particles of the type described above contained in the oil in a finely-divided state are also associated with larger particles which are no problem from the standpoint of reclamation operations whereby they may be readily removed by such well-known means as filtration. The finely-divided particles, e.g. those less than 5 microns, and frequently those between the particle size range of 150 millimicrons and up to about 1-2 microns, are extremely resistant to removal by mechanical means such as filtration, centrifugation, magnetic separation and the like. Were it possible to increase the particle size of these particles by agglomeration technique, they could readily be removed by a conventional reclamation operation. To accomplish this removal, the invention contemplates treating such contaminated oils after they have been separated from the water phase where they have been used as an emulsion by adding thereto at least 50 parts and preferably 200- 1000 ppm. of a trimerized polycarboxylic acid formed by the polymerization of a polyolefinic fatty acid which contains at least carbon atoms in an aliphatic chain.

The trimerized polycarboxylic acids used in the invention are formed by the heat polymerization of polyethenoid unsaturated fatty acids, such as A-9,10,11,12-octadecadienoic acid. These acids are capable of polymerization in accordance with the teachings of US. 2,482,761 and US. 2,763,612. These patents are directed to polymerizing such acids to provide as the main product socalled dimerized fatty acids which contain approximately 2 carboxylic acids per unit. As a result of distillation of the dimer acid, there is a pot residue which remains which is composed primarily of the trimerized fatty acids utilized in the practice of this invention. Considerable evaluation of the structures of these materials has been undertaken, and even though much has been postulated as to their chemical composition, the exact structure of the trimerized polycarboxylic acids which result from the dimerization of fatty diethanoid acids is not entirely clear.

A typical trimerized fatty acid useful in the practices of the invention is the commercial material, Empol 1040 trimer acid. This material is sold commercially by Emery Industries, Inc. This particular material may be considered as a C long chain tribasic acid with 3 or more alkyl side chains and two unknown linkages. This acid results as a still bottom from the polymerization of two C diunsaturatcd monobasic acids which form as the basic product a C dibasic acid.

A generic structure for the trimer acid, Empol 1040, is presented below.

In the above structure, the R R and R groups are alkyl side chains within the molecule and X are undetermined linkages resulting from the polymerization of three unsaturated fatty acid molecules that from the trimer acid. The material as supplied contains approximately by weight of a trimer acid with a slight contaminant being about 5% by weight of residual monobasic, and in some instances dibasic, polymerized fatty acids. The characteristics and properties of this material are presented below in Table I.

TABLE I Typical Speeificharac- Property cation teristic Test method Acid Value 183-191 AOOS Method To la-64T. Saponification Value 192-200 AOCS Method T1 1a-64T. 'Irirner content, percent 90 Dimer content, percent 5 Color Specific gravity, 25I25C 0. 9750 Specific gravity, 50/25C 0. 0490 Specific gravity, l250 0.9300 Pour point, F 77 Flash point, F-.. 505 Fire point, F 680 Viscosity, cs, 50 O 11,300 Viscosity, 05., 75 0.. 1, 790 Viscosity, c.-., 100 C 395 Refractive index, 25 1. 4967 Refractive index, 50 C. 1. 4891 Ash, ppm 100 Unsaponifiable content, percent 0.32

1 Dark brown.

NOTE.Trimer acid ls soluble in alcohol, ketones, and ethers and is partially soluble in mineral spirits.

As indicated, the trimer acids of the type described are used to treat finely-divided lubricating oils contaminated with finely-divided components which are primarily metallic in nature, which treatment is accomplished by subjecting the oils to a mixing step, preferably at elevated temperatures. The degree of agitation need not be great and may be considered that amount suflicient to provide uniform admixture of the trimer acid with the contaminated oil for a period of time to cause particle growth to occur. The time of agitation is, of course, dependent upon the speed of agitation, the nature of the oil treated and the contaminants contained therein. Usually, as a general rule, mild agitation which is visible to the eye may be employed for a period of time ranging from as little as 5 minutes up to as long as 1 hour 01' more depending upon the amount of chemical used, temperature of the system, the conditions of the oil, the amount of contaminants, the particle size range and the like. All of these variables may be readily correlated by routine experimentation of the type frequently conducted in determing optimum coagulation conditions for aqueous systems wherein they are treated with such Well-known coagulants as alum.

The temperature at which the oils are treated with a trimer acid should be in a preferred embodiment of the invention at least 100 F although it will be understood that room temperature or lower temperature ranges may be employed without departing from the spirit of the invention.

In a preferred embodiment, contaminated rolling oils are treated at a temperature within the range of about -200 F., with the preferred temperature range being within the range of from about 17() l90 F. As a general rule, the higher the temperature, the shorter the contact time to afford agglomeration of the particles, and the greater will be the success in agglomerating the finely-divided metal particles.

After the particles have been subjected to the agglomeration step, the oil is then removed and subjected to conventional purification treatments with a particularly preferred treatment being filtration. With the particles being in an agglomerated state, they are more readily removed by the filters, thus allowing a much more purified oil to be furnished from the filtration step which may be reutilized in metalworking operations.

Examples In order to illustrate the benefits obtained by the invention, a typical metalworking emulsion was obtained from a rolling operation. The emulsion comprised 90% water with being a contaminated metal rolling oil. This oil had the following composition at the time it was placed into the emulsion system.

Ingredients: Percent by wt. Tallow triglyceride 2'5 Nonly phenol-Rx 10 moles ethylene oxide 1.5 Nonyl phenol Rx 4 moles ethylene oxide 1.5 Mineral oil 72 The above emulsion which contained this oil was allowed to stand for several hours, at which time the oil separated from the water phase. This was skimmed and placed into a small laboratory beaker. It was estimated that the oil contained about 5% by weight of water. To the oil was added 200 p.p.m. of Empol 1040 and the beaker subjected to mild agitation, with a small laboratory stirrer. During the agitation, heat was applied to the beaker from a steam cone and the agitation was continued for about minutes, at which time the temperature of the beaker had risen to 120 F. At the end of this time, visible agglomerates formed throughout the oil. The oil was removed [from the steam cone and was passed through a small laboratory sand filter. The oil removed from the filter was sparkling clear and was readily emulsified with 85% by weight of water and was capable of being reused for the rolling of steel.

A comparative test was run on the Water separated oil which had not been subjected to the agglomerating step. The oil coming from the filter, although relatively clean in appearance, was determined to still contain many minute particles of metals and metal oxides which rendered it not entirely satisfactory for reuse in the metalrolling operation.

From the above it is seen that a new concept in the treating of lubricating oils used in the working of ferrous and non-ferrous metals has been aiforded. As an adjunct to conventional cleanup procedures used to treat such oils, it affords improved economies to the metalworking industries.

Having thus described my invention, it is claimed as follows:

1. A process for purifying and reclaiming lubricating oils used in a water emulsion in the working of ferrous and non-ferrous metals, wherein such oils are contaminated with finely-divided suspended solids exemplified by finely-divided metal particles, finely-divided metal oxides and dirt which comprises the steps of treating said oils with at least p.p.m. of a trimerized polycarboxylic acid formed by the polymerization of a lpolyolefinic fatty acid which contains at least 10 carbon atoms in an aliphatic chain, mixing the lubricating oil and trimerized polycarboxylic acid for a period of time to cause, by agglomeration, an increase in the particle size of the finelydivided suspended solids, and then removing the thus agglomerated particles from said lubricating oil.

2. The process of claim 1 where the trimerized polycarboxylic acid is formed by the polymerization of A-9,l0, 1 1,12-octadecanienoic acid.

3. The process of claim 1 where the amount of trimerized polycarboxylic acid used is within the range of from 200-1000 p.p.m. and is a trimer acid characterized as containing 54 carbon atoms and 3 carboxylic acid groups and the temperature at which the agglomeration takes place is at least F.

4. The process of claim 3 when the agglomerated particles are removed from the oil by filtration.

References Cited UNITED STATES PATENTS HERBERT LEVINE, Primary Examiner.

US. Cl. X.R. 252-49.5, 57 

